Diablo was not the best RPG there is and it never will be because it's not an RPG.
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I'm not sure the correct title for Diablo or Diablo 2 except a "Run around and kill stuff game."
There are several implications that Diablo 3 will exist, but because we don't know anything for sure, there's an equal chance that it won't exist, or that it may become a full fledge MMORPG.
Now, I did like the diablo series, I didn't love it, I wasn't addicted, I liked it. Adding a story and flavor to it would be nice, it'd definitely catch my attention. But if they make it another of the same ol' same ol', or worse, an MMORPG, Blizzard has lost pretty much all my respect.
From what I've seen, the MMO's of today are really not at all appealing, most of it is just running around and killing things, most commonly going player versus player, which I despise.
If they do decide to create an RPG of Diablo, then they've "woo'd" me, and nothing more. I've never really been impressed with diablo, but that's just me.
So I'm leaving my vote for your poll pretty much undecided, for reasons of the above, as well as the neutral vote you presented also does not have RPG's aside from -maybe- fallout.